Active matter systems constitute a type of matter whereby each unit particle utilizes energy to generate work [1]}, [2]}, [3]}. There are many examples of active matter systems from both living [4]} - cells, animals etc - and non-living contexts [5]} (molecules, droplets, grains etc) in the world around us.
The energy required for movement can either be self-generated (as in the case of cells in biological tissues which convert stored energy into motion) or as in driven granular systems supplied externally by a shaking plate. As each particle (or `agent') utilizes energy at the individual level, active matter systems are out of equilibrium at the single particle scale [6]}.
